The applicant's European Patent Specification No. 0122710 discloses a microwave oven which delivers microwave power to the oven cavity simultaneously with thermal power provided by a circulation of hot air forced through the cavity by a fan. A temperature sensor (sensing temperature of the hot air) and a timing means monitor the temperature/time variation. If a predetermined maximum temperature (e.g. 250.degree. C.) of the hot air is reached in a predetermined time (e.g. thirty minutes) from commencement of cooking with the oven in a cold condition, the oven automatically switches off to finish the cooking process. Most food items other than large meat or casserole dishes will be cooked within the predetermined time by this method. For larger meat and casserole dishes, where the maximum temperature is reached after the predetermined time, the delivery of microwave power is increased and the delivery of thermal power is decreased when the maximum temperature is reached in order to complete cooking of these denser food items. For such denser food items, the hot air temperature decreases with time after the predetermined time has elapsed, but the curve has a small (negative) slope which means that inaccuracies can arise if the end of cooking is determined by the temperature dropping to any set level.
The present invention relates to a modified method of cooking such denser food items which do not reach the predetermined maximum temperature within the predetermined time, the aim of the modification being to increase the slope of the temperature/time curve during the final stage of cooking to make switch-off more precise in time.